The invention relates to a synchronous operation safeguard for transfer stations for devices for handling containers, in particular for handling bottle-like containers made of glass or plastic with a first and a second rotary element, each of which is provided with receiving elements for the containers and in each case comprises a motor drive, wherein the rotary elements are arranged relative to one another so that the containers in a transfer region can be transferred from one of the first receiving elements to one of the second receiving elements.
The invention, furthermore, relates to a device for blow-molding containers made of a thermoplastic material with at least two treatment stations with tools for receiving and holding preforms, for example a heating device for heating the preforms, and a blowing device for forming containers from preforms, which device is provided with blowing stations, with at least one transfer device for the transfer of the preforms from a treatment station to a further treatment station with tools, which are designed for removing the preforms from the treatment station, for the transport of the preforms to the further treatment station and for passing the preforms on to the further treatment station, wherein at least one of the treatment stations and/or the at least one transfer device comprise at least one mechanical control device for defining the movement of the tools, wherein the tools in their movement relative to one another have an engagement region and are arranged relative to one another so that the movement of the tools during normal operation takes place without contact, and wherein the drive of the movement of the tools of the treatment stations and/or of the transfer device takes place by means of individual drives, which are synchronized in terms of control and a method for securing tools for transporting preforms or containers, preferably mandrels or grippers, in such a device.
For packaging liquid foodstuffs and beverages, containers are used. These are in particular bottles made of glass or plastic or so-called pouches, but in this application, containers is to also mean preforms, closures or the like. The containers are produced in a production process in different devices and subsequently filled at a further device. During the production and filling process it is necessary to transport and transfer the containers between the individual process stages from one station to the other.
The production of containers made of plastic in a blowing device is mentioned as an example here. During a container molding through the effect of blowing pressure, preforms of a thermoplastic material, for example preforms made of PET (polyethylene terephthalate) are fed to different processing stations within a blowing machine. Typically, such a blowing machine comprises a heating device and a blowing device, in the region of which the previously temperature-controlled preform is expanded into a container by way of biaxial orientation.
The expansion is effected with the help of compressed air which is introduced into the preform to be expanded. The process sequence during such an expansion of the preform is explained in DE-OS 43 40 291. The introduction of the pressurized gas mentioned at the outset also comprises the pressure gas introduction into the developing container bubble and the pressure gas introduction into the preform at the start of the blowing process.
The fundamental construction of a blowing station for container molding is described in DE-OS 42 12 583. Possibilities for temperature controlling the preforms are explained in DE-OS 23 52 926.
Within the device for blow-molding, the preforms and the blown containers can be transported with the help of different handling devices. The use of transport mandrels onto which the preforms are plugged has proved itself in particular. However, the preforms can also be handled with other support devices. The use of grippers for handling preforms and the use of spreading mandrels, which for holding can be introduced into a mouth region of the preform, likewise are among the available designs.
Handling of containers using transfer wheels is likewise described in DE-OS 199 06 438 with an arrangement of the transfer wheel as transfer station between a blowing wheel and an output route.
Originally, the transport devices in such a processing machine, in particular ones that had to cooperate at high speed highly accurately, for example divisionally precisely or cooperate synchronously, were coupled to one another in a purely mechanical manner. For example, the inlet and outlet stars of a filler or a labeling machine were connected to one another rigidly, that is “divisionally correctly” by way of direct, non-slip drive connection, i.e. by way of gear wheels, toothed belts and toothed belt pulleys. With this solution, a fault, for example a power failure, merely resulted in a machine stoppage but not in a loss of the synchronous operation of the interconnected machine components.
For cost reasons, a rigid coupling is omitted, as a result of which expensive, assembly-intensive and hard-wearing transmissions, universal shafts etc. can be omitted. Instead, the individual components such as for example inlet star, outlet star, rotor of the treatment machine etc. are in each case provided with separate drive motors, the drive motors being for example servo-motors, which are preferentially equipped also with rotary position transducers. Rotary position transducers feed the actual angle of rotation back to the control. In the case of deviations between set and actual angle of rotation, a correction takes place automatically so that the motor reaches the set angle of rotation. This applies to “static” positioning tasks, in the case of which a motor is to reach a set angle of rotation and then remains without further rotary movement until a renewed change of the set angle of rotation occurs. Furthermore, this applies also to “dynamic” positioning tasks, in the case of which rotary movements are to proceed with one another simultaneously and synchronously to one another over several hours.
In the presence of a fault, the rotary element that deviates from the rotary synchronicity is switched so as to be without drive and so as to be freely rotatable. At the same time, the entire plant is brought to a halt. Through the presence of the residual energy that is inherent in the released rotary element, which is removed more slowly than that of the actively braked rotary element, “overtaking” by the released element and thus a collision can occur.
In order to avoid damaging the machines and production failures connected to this, either the synchronicity of the movements has to be ensured not only in the operating state but has to be absolutely maintained even during faults such as power failure, sudden load fluctuations etc. or damage has to be avoided in another way.